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Water Washing Biodiesel 101

Introduction:
While dry washing Biodiesel is starting to gain popularity, water washing is still king. So, being that it’s such a popular method for cleansing reacted Biodiesel, it’s about time we did an article on how to water wash Biodiesel to ensure you have properly washed all the contaminants out of the Biodiesel.

Why It’s So Popular & How It Works
Water really likes to dissolve whatever it comes in contact with. That includes soap, methanol, glycerin, and other contaminants commonly found in freshly reacted Biodiesel. When done properly, it can cleanse the Biodiesel extremely well. Here’s why…

It Removes Methanol Like No Other
Methanol likes bonding to water much more than it likes bonding with oils, such as Biodiesel. So, when water is introduced, the methanol latches on to it like crazy and as the water falls through the Biodiesel (because water & oil don’t really mix all that well), the water pulls the methanol right along with it. Not even ion exchange towers are this good at removing methanol!

It Dissolves Soap Extremely Well
Whenever we shower or wash our hands, we use soap. One of the reasons for this is because the soap likes to bond with the water and come along for the ride. In the case of washing our hands, the soap also pulls oils right along with it and removes the oil & grit from our hands. This is the same with Biodiesel. As we gently mist a spray of water over the reacted fuel, the soap will bind to the water molecules and fall out of the Biodiesel much more readily than just settling alone. Soap is kind of tricky though in that it also is an excellent emulsifier and if the water is sprayed too hard, we can create emulsions in the Biodiesel…more on that issue later.

It Removes Additional Contaminants
Glycerin, excess catalyst, dirt, grime, flour particles, and anything else that’s left over from the oil getting reacted into Biodiesel doesn’t stand a chance when water is used as a means to cleanse the fuel. This is again due to waters great ability to dissolve things and then pull them along for the ride as it falls to the bottom of the tank.

Dry wash resins, magnesium silicate powders, wood chips, vacuum pumps, or other means of cleansing Biodiesel just can’t hold a candle to the all encompassing power of good old water. While dry washing techniques have their place, they often have to be combined with several other technologies to completely cleanse the fuel as well as water does. Can you see where this is going?

So, here’s some tips on how to use water to cleanse your Biodiesel squeaky clean.

Tips & Tricks For Successful Water Washing1) Before you attempt to water wash, be sure your fuel is reacted
– Well reacted Biodiesel just washes better. It’s because there’s less oil and more Biodiesel in the mix and Biodiesel washes better than oil will.
– To test the fuel, run a simple 3/27 Biodiesel Conversion Test.The example on the left shows a pass (left) and a failed test (right).

When re-reacting, a good rule of thumb is to use 30% of the original catalyst & methanol. Be sure to heat the fuel back up too before re-reacting. Reactions LOVE heat.

2) To Wash Biodiesel, You’ll Use Approximately The Same Amount Of Water As The Fuel You Need To Wash
– For example, if you are washing 50 gallons of Biodiesel, expect to go through 50 gallons of water. How much exact water used will depend on how aggressive the water spraying is, how warm the Biodiesel is, how hot the water is, and how dirty the fuel is. All of these factors can influence the amount of water required to wash.

3) Don’t Spray Too Aggressively At First. It’s Bound To Make A Mess
The first wash is the one that you have to be the most careful with. Spray too aggressively and it’s bound to emulsify the soap into a goopy mess. In general, if you have a manual mist-washing system, heat up the Biodiesel, turn on the misters, and then carefully watch the Biodiesel to make sure an emulsion isn’t starting to form (it’ll look like a whitish yellow milk shake. It starts off looking kind of like skim milk and can develop into what looks like cottage cheese or mayonnaise.

Emulsion can be broken using salt water and can be prevented by adding a little vinegar to the water, but the best way to keep them from happening is by going fairly easy with the water on the first wash cycle. You’ll notice that the first wash water will always seem to be the most cloudy and white. This is due to water working it’s magic and removing the soap. Over time you’ll discover just how hard you can spray with the first wash, but I always recommend going as easy as you can on the first wash cycle & get more aggressive with the spray on the subsequent washes.

4) In General, Do At Least 2-3 Mist Wash Cycles And Then Check Soap Levels. Continue To Wash Until The Soap Is Completely Removed.
Biodiesel will vary in the amount of soap produced during the reactions. Typically, the higher the titration, the more soap is going to get produced. More soap means longer wash times to get it all out. But in general, usually 2-3 mist washes will get the majority of the soap out.

To check for soap, start off by doing what’s called a “Shake-Em Up” test. Basically, fill a jar half-way full of the washed Biodiesel, then fill the rest of it with water. Cap it and then shake the living crap out of it. Then, let it settle for about 20-30 minutes. Return and check the clarity of the water on the bottom. If it’s still hazy & cloudy, you still need to continue washing.
If it’s nice & clear, then you’re almost there! The next step is to do a full-blown soap titration test on the Biodiesel to see if all the soaps are removed. This is done by using a Soap Testing Kit.

You can make one of these up yourself by purchasing all the chemicals and equipment needed, or stop by our site and check out our handy Soap Testing Kit.

Once all the soaps are removed from the Biodiesel, then it’s time to start drying the fuel.

5) When Drying, Heat, Circulation, And Air Flow Are You’re Friends
There are several ways to dry the washed Biodiesel. The most common being just plain old heat & time. Followed next by bubbling air through the fuel. However, one of the most effective ways to dry Biodiesel is by both heating AND circulating the fuel back on top of itself. Click here to see a really nice Biodiesel drying setup.

Adding a fan to blow across the top also will speed up the drying process as well.
photo of wash tank from BiodieselPictures.com

We stock a nozzle called a Dry Pro that is great for this type of application. Whether you use a nozzle like this, a shower head, or even just a hose with a bunch of holes punched through it draped over the top of your barrel, the goal is to spray the fuel back on top of itself to air it out. You can read more about this drying technique at the Collaborative Biodiesel Tutorial website. Click here to see the article

There are several ways to check to see if it’s finished drying, but the quickest test is by using the hot pan test. Click here to see a video of this test. Basically, heat up a pan, then drop in about 30 mL of Biodiesel. Then watch for bubbles or steam. If you don’t see any, your fuel is dry!

When water washing Biodiesel properly, the end result can be extremely well cleaned Biodiesel that is ready to use!

So there you have it, our tips for water washing Biodiesel to get it nice & squeaky clean and dried! Go Bio!

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